8 THE STRUCTURE OF FLOWERS. 



table to the law of compensation, in consequence of tlie 

 enhanced growth of the corolla, the petals thereby abstract- 

 ing the nourishment that would be required by the stamens 

 superposed to them. 



That the number of staminal whorls should be two in 

 verticillate flowers, i.e., equal to the perianth, is apparent 

 from the fact that two whorls prevail in Monocotyledons and 

 are not at all uncommon in Dicotyledons ; and when the 

 petaline whorl alone exists, as in PrimulacecB and Myrsinece, 

 calycine staminodia are sometimes present which tend to 

 restore the complete number, as in the genus Samolus in the 

 former and in the tribe Theophmstece of the latter order. 



The reduction of the number of carpels is very generally 

 carried to a greater extent than that of the stamens. Assum- 

 ing two complete whorls of carpels as the primitive number, 

 not only are both rarely to be found in the same flower, as 

 in Bidomus, but a portion only of one whorl is commoner 

 than even a single entire whorl. Thus, two are characteristic 

 of Cruciferce, Polygalece, and of most of the gamopetalous 

 orders ; while one carpel only prevails in Leguminosce and 

 elsewhere. 



That the absence of parts of, as well as of entire whorls 

 of flowers as they now exist does not represent primitive 

 conditions, is testified to by the frequent occurrence of 

 various kinds of degradations, such as were alluded to above in 

 the case of the staminodia of Samolus, etc. Thus, with regard 

 to the calyx, it is a noticeable fact that when the inflorescence 

 consists of a large number of flowers, especially if small and 

 closely compacted, there is a strong tendency for the sepals 

 to become partially arrested and remain rudimentary, or even 

 not to be developed at all. This, is particularly observable 

 in some epigynous orders as JJmbelliferce, Araliacece, Capri- 

 foliacece, Rubiacece, Composite, etc. 



